Postpartum Pulmonary Embolism

Postpartum pulmonary embolism is blockage of the pulmonary arteries by a clot, usually from the leg or pelvic veins, in the 6 weeks after birth. It is an important direct cause of maternal death in the puerperium, and risk peaks in the first 2 weeks, mostly after caesarean section. It matters because recognition and anticoagulation within hours prevent death.

• Risk factors: caesarean section, immobility, postpartum haemorrhage, preeclampsia, infection, body mass index above 30 kg/m2, age above 35 years, previous clot, thrombophilia, sickle cell disease, smoking.
• Untreated leg clots can embolise to the lungs.
• Massive embolism causes sudden collapse.

Women have sudden breathlessness, pleuritic chest pain, cough, haemoptysis, palpitations, light headedness and sometimes syncope or leg swelling. Large emboli cause shock and cardiac arrest.

• Respiratory rate above 20 per minute, pulse above 100 per minute, oxygen saturation below 94 percent.
• Raised jugular venous pressure, loud second heart sound, signs of leg clot.
• Differential diagnosis: peripartum cardiomyopathy, pneumonia, amniotic fluid embolism, pulmonary oedema from preeclampsia, asthma, pneumothorax, sepsis, anaemia, anxiety, acute coronary syndrome, aortic dissection.
• Complications: right heart failure, cardiogenic shock, cardiac arrest, chronic thromboembolic pulmonary hypertension, recurrent embolism, bleeding on treatment, maternal death.

The approach is clinical probability, with resuscitation first for the unstable woman and imaging for the stable one.

• Pulse oximetry, blood pressure, ECG (sinus tachycardia, right heart strain), chest X-ray (to exclude other causes), arterial gas if saturation is low.
• CT pulmonary angiography is the test of choice; ventilation perfusion scan if CT is not possible or kidney function is poor; bedside echocardiography for right ventricular strain in the unstable woman.
• Compression ultrasound of the legs (a clot allows treatment without further imaging).
• Full blood count and platelets, creatinine, troponin, brain natriuretic peptide, prothrombin time, activated partial thromboplastin time and group and save before anticoagulation; D-dimer is not reliable after birth.

The principle is immediate anticoagulation on suspicion, resuscitation for shock, and thrombolysis for massive embolism.

• Supportive: sit up; oxygen 10 to 15 L/minute by mask to keep saturation at 94 percent or above; two large-bore cannulae; Ringer's lactate 250 to 500 mL only if the pressure is low without heart failure; high dependency care with continuous monitoring; breastfeeding continues when stable.
• Pharmacological: enoxaparin 1 mg/kg subcutaneous 12-hourly for at least 3 months and not less than 6 weeks after birth; unfractionated heparin 80 units/kg IV bolus then 18 units/kg/hour adjusted to an activated partial thromboplastin time of 1.5 to 2.5 times control for massive embolism, shock or creatinine clearance below 30 mL/minute; alteplase 10 mg IV bolus then 90 mg over 2 hours (maximum 100 mg) for shock or cardiac arrest, followed by unfractionated heparin; warfarin 5 mg oral once daily from day 1 with enoxaparin overlapping for at least 5 days until the INR is 2.0 to 3.0 on 2 readings 24 hours apart; noradrenaline 0.05 micrograms/kg/minute IV titrated to a mean arterial pressure of 65 mmHg or more; paracetamol 1 g oral 6-hourly (maximum 4 g in 24 hours) for pleuritic pain.
• Procedures: catheter directed thrombolysis or thrombectomy, or surgical embolectomy, for shock when alteplase fails or is contraindicated; inferior vena cava filter if anticoagulation is contraindicated or clot recurs; extracorporeal support in referral centres.
• Special groups: renal impairment uses unfractionated heparin; recent surgery or ongoing postpartum bleeding needs a senior decision on thrombolysis, using catheter or surgical removal where possible; platelets falling by 50 percent after day 5 of heparin suggest heparin-induced thrombocytopenia and need fondaparinux 7.5 mg subcutaneous once daily (weight 50 to 100 kg) under specialist advice; heparin and warfarin are compatible with breastfeeding and direct oral anticoagulants are avoided.
• Red flags: systolic blood pressure below 90 mmHg, syncope, oxygen saturation below 90 percent, raised troponin, right ventricular strain on echocardiography, bleeding, platelets falling.
• Follow-up: platelets on days 7 and 14 of heparin; INR twice weekly until stable; review at 6 weeks and 3 months; echocardiography at 3 months if breathlessness persists; thrombophilia testing at 3 months; heparin prophylaxis in any later pregnancy and for 6 weeks after birth.